Devices for unwinding and winding one or more lines are generally known, but they have various disadvantages depending on the particular application.
“Cable drums” (actually cable reels) have the disadvantage, for example, that although power is supplied via continuous lines, for the purposes of unrolling or rolling, the connections to the drum have to be disconnected in order to prevent twisting of the connected lines, since the plug connections are connected to the drum and thus also rotate during the winding process.
With “automatic cable reels” or “spring operated cable reels”, disconnection of the plug connections during the unwinding and winding operation is unnecessary since connection is achieved within the reel by way of sliprings or sliding contacts. However, due to the underlying principle, this leads to elevated mechanical wear and/or increased susceptibility to soiling. In the case of liquid-conveying lines too, tightness of the rotary joints must be ensured over extended service cycles.
Moreover, it is not always feasible to use sliprings or rotary joints. On the one hand, the use of sliding contacts is out of the question in many fields, for example in signal transmission, since sliding contacts would here lead to significant impairment. On the other hand, such a solution is also technically very complex in cases where a relatively large number of lines or a mixture of a plurality of electrical and liquid-conveying lines have to be linked together reliably via sliprings or rotary joints. Furthermore, it is largely impossible in this case to achieve a compact and/or economical embodiment of the reel.
To get round the use of sliding contacts, solutions are additionally known in which a line is guided continuously over two drums, one being stationary and one rotatable. As the usable part of the line is unwound from the rotatable drum, another part of the line is wound around the stationary drum. Although such solutions do not require any unplugging of the connections during the winding process, in particular winding on the stationary drum often causes problems due to distortion and the formation of loops in the line. Moreover, such devices would appear to be unsuitable for guiding a plurality of lines.
Finally, it would be desirable, with measurement, control and automation technology becoming ever more sophisticated, for it to be possible (optionally even subsequently) to convey data or signal lines in a single device in addition to the conventional application lines.